Cathartics: Magnesium sulphate, Sodium orthophosphate, Kaolin and Bentonite : Pharmaguideline

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Cathartics: Magnesium sulphate, Sodium orthophosphate, Kaolin and Bentonite

During a catharsis, the bowels (intestines) are cleansed, purged, or evacuated. Cathartics or purgatives are agents that stimulate catharsis.


During a catharsis, the bowels (intestines) are cleansed, purged, or evacuated. Cathartics or purgatives are agents that stimulate catharsis; they are more commonly known as laxatives (for instance, a cathartic used to relieve constipation). Defecation is accelerated with cathartic substances in medicine. The laxative effect occurs by softening the feces, which is similar to the effects of peristaltic motion. Cathartic and laxative properties are capable of being combined in the same substance. Nonetheless, psyllium seed husks contribute to an increase in feces bulk. As a form of gastrointestinal decontamination after ingestion, cathartics like sorbitol, magnesium citrate, magnesium sulfate, and sodium sulfate were commonly used. The use of these medicines for poisonings has decreased over the years. Cathartics at high doses can be effective for removing toxins from the lower gastrointestinal tract; however, dehydration and electrolyte imbalances can occur as a result. When exposed to pesticides, such as elemental sulfur, one can experience catharsis.

The categorizations of cathartics are as follows:
  • Bulk cathartics increase the volume of the stool (feces) to stimulate the bowel's evacuation. There are many sources of dietary fiber, including psyllium husk, methylcellulose, wheat bran, and oat bran.
  • Having lubricants and emollients soften the stool and reduce friction between it and the intestinal wall, they can act as cathartics. Glycerine (as a suppository) and mineral oil (as a topical) are examples.
  • Water is added to the feces by osmosis to increase their weight and water content. Osmotic cathartics can be divided into two categories:
  • There are several salt-based cathartics (Saline cathartics) available, including magnesium hydroxide, sodium sulfate, magnesium sulfate, and magnesium citrate.
  • The disaccharide sorbitol, a sugar that is fermented in the intestine, provides stool bulk.
  • The muscular contractions caused by stimulant cathartics allow the contents of the intestines to be expelled.
  • Among those mechanisms, combination agents are embedded.

Magnesium sulfate

Molecular formula – MgSO4, MgO4S
IP limit - About the dried substance, it should contain no less than 99.0% and no more than 100.5% magnesium sulfate.

Properties - Prisma's are colorless crystals formed by it. Despite its solubility in water, it is largely insoluble in alcohol. The taste is saline-bitter but cooling.

  • Sulphuric acid can be neutralized with magnesium or magnesium oxides or carbonate by heating it. Filtering results in a concentrate and recrystallization of the filtrate.
  • To make it commercially, sulphuric acid is reacted with dolomite. So formed magnesium sulfate dissolves in the solution, making sparingly soluble calcium sulfate a solid deposit. To concentrate the liquid, it is crystallized after it has been filtered.
In the treatment of pre-eclampsia and eclampsia, magnesium sulfate is used as a cataphoresis, as an electrolyte replenisher, and as an anticonvulsant. Myometrial muscle cells are directly inhibited by the compound. During contractions, contraction frequency and force decrease due to uncoupling between excitement and contraction.

MOA of magnesium sulfate

The intracellular fluids contain a cation called magnesium that is the second most abundant in the cells. Several enzyme systems rely on it for their activity and it plays a crucial role in neurochemical transmission and muscle excitability. A decrease in the release of acetylcholine at the myoneural junction is accompanied by a decrease in the contraction of striated muscle and peripheral neuromuscular transmission when magnesium sulfate is administered. Magnesium also inhibits Ca2+ influx through voltage-dependent, dihydropyridine-sensitive channels. These are responsible for most of Magnesium's relaxing effects on vascular smooth muscle.

Sodium orthophosphate

Sodium orthophosphate the dodecahydrate of dibromo-propane dihydrate. A minimum of 98.5% and a maximum of 101.0% Na2HPO4 is present in it.

The molecular weight is 358.14

  • It can be obtained by combining sodium carbonate with the hot phosphoric acid solution.
H3PO4 + Na2CO3 —> Na2HPO4 + H2O + CO2

By centrifuging, washing, and drying the crystals, a neutralized solution is concentrated and separated.
  • Calcium sulfate can also be produced by treating calcium phosphate with sulfuric acid, resulting in monobasic calcium phosphate.
Ca3 (PO4)2 + 2H2SO4 —> Ca (H2PO4)2 + 2CaSO4

  • As dibasic calcium phosphate is deposited in the filtrate, sodium phosphate is now dissolved in sodium carbonate.
Ca (H2PO4)2 + Na2CO3 —> CaHPO4 + Na2HPO4 + CO2 + H2O

A filter is used to remove the solution. Concentrating the solution and crystallizing it produces crystals of sodium phosphate.

Dose – a normal dose includes 2 to 16 grams of sodium orthophosphate.

A tightly closed container is used for storage.

Properties - Having a saline taste, this substance appears as transparent, colorless crystals. The material is odorless and effervesces in an atmosphere. Water can dissolve it, while alcohol cannot. It becomes sodium pyrophosphate when heated over 3000 C.

2 Na2HPO4 —> Na2P2O7 + H2O

Uses - It contains cathartic properties and works as a buffer and additionally it is used as a saline laxative.

Kaolin (Al2O3.2SiO2.2H2O)

Upon drying, it becomes mainly impurities-free as it is a native hydrated aluminum silicate.

Preparation - Using a system of electrical sedimentation, it is made by powdering and separating natural clay particles. To prevent contamination with gritty particles, it must be purified.

Properties - Powder is white and smooth with no gritty particles. The product is tasteless and odorless, and it gives off a soapy or greasy feeling.

Dose – a normal dose for kaolin is considered to be 15- 75 grams.

Storage - The product is kept in a well-closed container.

Uses - Dysentery, diarrhea, colitis, cholera, and other symptomatic conditions are treated with this mixture. It is used to treat poisoning caused by foods and alkaloid toxins by adsorbing the toxins. Along with this, it is also used in cosmetic preparations as well as dusting powders.


Properties - It looks like a fine, light cream or pale powder. A slight earthy taste accompanies the odorless and grit-free profile. A neutralization reaction increases its volume by about 12 times. It is almost insoluble in water.

Uses - It is used to stabilize emulsions as a protective colloid and as a pharmaceutical aid. However, its primary purpose is to suspend insoluble powders. For oil in water emulsions, it serves as an emulsifier. In addition to its use in pharmaceutical preparations including plasters and ointments, it is used as a base for many foods. It can be found in calamine lotions as a protective agent.

It comes from the hydration of aluminum silicate colloidally. Natural resources are used to obtain it. There is some sodium and potassium in bentonite, along with Al2O3, CaO, SiO2, MgO, and Fe2O3.
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